The virus did not creep toward San Jose firefighters. It lurked among them.

It was March 6, a week after the country’s first community-transmitted COVID-19 case at a Vacaville hospital. Exposure to the virus remained largely linked to overseas travel. California’s case count had just scraped triple-digits.

Quietly and without realizing it, a busy San Jose firefighter had carried coronavirus to his fire station. He covered a shift for a buddy at another firehouse, exposing colleagues there. He attended a career development course at the department’s training center — and the disease spread further.

Within the week, about 10 percent of the workforce had been exposed. Fifteen San Jose firefighters tested positive — the largest known cluster among Bay Area first responders and a wake-up call, even for those who thought they’d seen it all. Chief Robert Sapien realized, “this is not something we’ll be able to see or know in terms of where the virus is. It really felt at that point like it was all around us.”

The cluster of San Jose cases illustrate the heightened risk police officers, firefighters and paramedics face both from the public they are sworn to serve — and from each other, working in professions that leave them unable to distance themselves from others, or from a silent, potentially deadly disease.

“This is something we can’t see, touch, feel, or wrap our brains around,” said Lt. Paul Liskey, of the Alameda County Sheriff’s Office.

The threat from within

Beginning in January, Bay Area firefighters, police, and paramedics watched as coronavirus became deadly in China, decimated parts of Europe and landed in Washington state. It seemed like a “slow and visible” rise in cases would eventually sweep through Santa Clara County, Sapien said.

The department stocked up on personal protective equipment, and dispatchers started asking 911 callers if they’d been overseas. Firefighters called to the airport donned extra protective gear.

But when the San Jose Fire Department realized one of its firefighters was infected, it was obvious that the disease wasn’t just a threat from abroad. And as clusters of COVID-19 cases emerged among other first responders — firefighters in Alameda and Contra Costa counties, police staff in Oakland, sheriffs deputies in Santa Clara County — departments across the region realized the same.

“For all the work we’d done to prepare our responders as they engaged patients in the community, we didn’t think our exposures would come internally,” said Sapien, a 30-year veteran with the department.

Because firefighters live, eat and work together, they’re particularly vulnerable to spreading infection to one another. In Oakland, for instance, the century-old fire station on International Boulevard is too small for social distancing. Lockers and other barriers divide the dorm-like sleeping quarters, but the kitchen and common areas are cramped. At shift change, as many as 15 firefighters could be at Station 4, jostling one another with nearly every move.

“There’s really no way for us to get around that; it can be quite a challenge,” said Lt. Dan Robertson, who works at the station.

Like other first responders, Robertson has changed his habits. Before leaving a shift, he showers and leaves his uniform in the firehouse. When he gets home, he showers again. Crews disinfect the station multiple times a day.

Inside ambulances, two responders likewise work in close proximity, sitting about three feet from each other on a call, said Jocelyn Paulson, a paramedic in Santa Clara County and union leader. When there’s a patient, a family member and a trainee, that number jumps to five, which has prompted paramedics to limit who can ride along.

An asthmatic who often gets allergies, Paulson vigilantly tracks any sneeze or cough to make sure she’s in shape to come to work. But “it’s a trust factor” that the person sitting next to her is doing the same, she said.

Those realities collide uncomfortably with new research out of China and Italy showing that people with mild or no symptoms of COVID-19 are the main drivers of the pandemic’s spread. That knowledge — along with concerns that PPE supplies might not last through projected surges of patients at local hospitals — has left many first responders feeling even more vulnerable.

“We, right now, don’t know how many people truly have COVID-19,” Paulson said.

“I’m the last person who wants to come down with COVID,” she added. “I have to put that down at the door and put the uniform on.”

‘A smokeless fire’

The novel coronavirus hit the San Jose Fire Department in a way no one expected.

On Feb. 28, the same day that Santa Clara County announced its first case from community transmission, a firefighter returned from a medical call to report a possible exposure. It turned out to be a false alarm — flu, not COVID-19.

But the relief lasted just a week. On March 6, the department got wind one of its own firefighters, whom the department is not naming, had been hospitalized with an illness soon confirmed to be COVID-19.

“That’s when things became very real for us in San Jose,” Sapien said.

First, department and health officials raced to track down the firefighter’s every recent contact. It was, as Sapien put it, “quite a few” people, from his own regular crew to those at a second station to fellow attendees at a training event. All of those contacts occurred prior to the firefighter developing symptoms.

On the morning of March 12, when Santa Clara County’s cases had ticked up to 48, San Jose officials lined up for a news conference at the airport to explain what was unfolding inside the fire department. Even as the news conference started, the number of exposed firefighters was in flux.

“I can tell you it’s in excess of fifty,” said City Manager Dave Sykes when pressed for an estimate. Someone in the audience gasped.

Within hours, officials confirmed that 80 firefighters had been exposed — and four had so far tested positive. They ordered a deep-cleaning of Fire Station 9 at 3410 Ross Ave., Fire Station 31 at 3100 Ruby Ave., as well as the fire training center at 255 South Montgomery St.

Even as some firefighters came back to work after negative tests, firefighters were instilled with a looming sense that the infection could be anywhere — or everywhere.

“It’s almost like sending firefighters to a smokeless fire — how do you know where it is?” Sapien said.

With 10 percent of firefighters exposed, the department scrambled to prevent more infections. Stations turned into medical laboratories, cleaned between shifts with disinfectant. Meantime, the department stocked up on thermometers to test employees outside the firehouse when they arrived for the start of a shift.

In the field, firefighters were told to take the “one-in” approach, with just one person — suited up in a mask, full gown and gloves — responding to those in distress initially to minimize contact and save precious gear.

Still, living in such close quarters, “it’s hard” for firefighters to prevent the spread of the disease, said Nick Jewell, professor of biostatistics at UC Berkeley School of Public Health, likening the department’s outbreak to those within households.

“It’s like a giant family, given they’re working in close quarters and having lots of contacts,” Jewell said. “This guy was out there, at risk, and bingo, he brought it back unbeknownst to himself, and there was some mixing in ‘the family.’”

The number of positive tests in San Jose crept upward. By March 16, the fire department counted 10 positive cases. At that point, county health officials said they would prioritize testing for first responders to “ensure we can stay as fully staffed as possible” across critical agencies.

By March 20, there were 13 cases. As of this week, there are 15, including two who have since recovered.

All but one of the positives have been linked back to the first patient or occurred during that initial period of spread, Sapien said. The public health tool providing that knowledge — known as contact tracing — has in the meantime been abandoned by the county as cases multiplied apace: In the three weeks since the fire department reported its first positive, Santa Clara County’s case count exploded from 66 to more than 1,000.

As of this week, the department was down to monitoring 28 people, including the positives — a steep drop since the initial 80 exposures. The rigorous cleaning, PPE and temperature-taking protocols will stay.

“We’re feeling like maybe this is a new normal,” Sapien said.

The ‘back door’

Last week, a deputy with the Santa Clara County Sheriff’s Office was grabbing dinner at a restaurant on Leigh Avenue in San Jose when he broke up a fight between a couple in a nearby alleyway. The woman was coughing and told the deputy she had the coronavirus, according to Sgt. Michael Low.

The deputy was transported away from the scene to disinfect gear, take a shower and change clothes, Low said.

That kind of person-to-person contact — a reality for most firefighters and patrol officers — puts first responders at greater risk of infection, epidemiologists say, and makes the disease a particularly dangerous double-edged sword for that group: As much as departments try to limit the spread of illness within their own buildings, employees still face exposure on the job.

“They are really our heroes because they’re putting their lives on the line,” said Dr. John Swartzberg, clinical professor emeritus of infectious diseases and vaccinology at UC Berkeley School of Public Health.

Already, departments have been hit hard. As of Friday evening, 196 Oakland police officers — or about 25 percent of the force — had been possibly exposed to the virus. Three have tested positive.

“It’s very worrying,” said Sgt. Barry Donelan, the president of the police union, “especially when you look across the country at New York. I’ve called over there. It’s a disaster.”

The New York Police Department this week reported about 5,600 officers were out sick and 1,200 had tested positive for COVID-19. At least two California law enforcement agents — a cop in Santa Rosa and two sheriff’s deputies in Riverside County — have died from the disease.

“I don’t know if we could take that kind of hit,” Donelan said.

The disease has also come with new demands: Between March 20 and March 31, Oakland police received 224 complaints of people violating the county’s COVID-19 shelter-in-place order, everything from a wig shop remaining open to two dozen people exercising in a parking garage, authorities said.

A veteran Oakland police officer, who spoke on condition of anonymity because she wasn’t authorized to speak to the press, said her days are now filled by calls for people suffering with mental health issues.

The officer was hit particularly hard by the fate of 43-year-old Santa Rosa police Detective Marylou Armer, whose death was announced Tuesday. The Oakland officer said she battles daily with whether to get tested, even though she has no symptoms.

“Day by day, it’s getting worse,” she said. “At first it was just older people, then it was only people with prior existing illnesses. Now, look at New York PD, and here in Santa Rosa — so close.”

“That scares me,” she added. “It’s in the back of my mind, but at the same time there’s nothing you can do about it, you still have to come to work.”

Many responders worry about endangering their families. Paulson, the paramedic, was relieved when her roommates left town three weeks ago to keep from sharing germs. Some colleagues have sent kids to live with another parent or grandparents, she said, or self-isolated in discounted hotel rooms.

At the same time, the risk of first responders bringing the virus back to work is “equally our Achilles’ heel,” said Menlo Park Fire Chief Harold Schapelhouman.

Two Oakland city officials shared the same story of a young firefighter defying the shelter-in-place order. In Oakland, one firefighter flew to Brazil on St. Patrick’s Day — the same day the Bay Area shelter-in-place order went into effect, said the sources. When he returned, his fellow firefighters urged him to go to a new testing site set up in Hayward. He tested positive.

In many Bay Area departments, firefighters live miles away from stations, visiting grocery stores and neighbors far afield from their colleagues. Menlo Park fire members on average live 60 miles from work, Schapelhouman said; in San Jose, about three-quarters of firefighters commute from outside the county.

“That back door is real. I don’t know what they are doing on their day off,” the Menlo Park chief said. “I can’t control that.”

Fiona Kelliher is a breaking news reporter at The Mercury News. She previously covered housing and real estate for the San Francisco Business Times. Originally from Minneapolis, she is a fan of almost any food that is fried and eaten on a stick.

David DeBolt is a senior breaking news reporter for the San Jose Mercury News and the East Bay Times of Oakland. Over the past decade, DeBolt has covered the deadly San Bruno PG&E pipeline explosion, police and government corruption, California wildfires and Oakland City Hall. He was part of the East Bay Times staff honored with the 2017 Pulitzer Prize for coverage of the Ghost Ship warehouse fire.

Alameda County Fire Department crews are at the scene of a fire that started about 5:30 p.m. Friday at the historic Lorenzo Theater at 16080 Hesperian Blvd. in the unincorporated community of San Lorenzo.